Rotary engine corrected for operating deviations



Sept. 9, 1969 c. JONES 3,465,729

ROTARY ENGINE CORRECTED FOR OPERATING DEVIATIONS 2 Sheets-Sheet l FiledApril 1, 1968 7 F56. Q A ML PRIOR ART INVENTOR. CHARLES JONES BYRW 2swam AGENT ROTARY ENGINE CORRECTED FoR OPERATING DEVIATIONS Filed April1, 1968 C. JONES Sept. 9, 1969 2 Sheets-Sheet 2 INVENTOR.

CHARLES JONES AGENT United States Patent 3,465,729 ROTARY ENGINECORRECTED FOR OPERATING DEVIATIONS Charles Jones, Hillsdale, N.J.,assignor to Curtiss-Wright Corporation, a corporation of Delaware FiledApr. 1, 1968, Ser. No. 717,569 Int. (Cl. F021) 53/00, 55/00 US. Cl.123-8 8 Claims ABSTRACT OF THE DISCLOSURE In a rotary engine of thetrochoidal type, bearing clearances and minor deflections of the shaftand rotor parts may cause apex seal wear and loss of pressure atportions of the operating cycle. This condition is corrected by mutuallyindexing the trochoidal housing and the rotor slightly out of phase.

Background of the invention Summary of the invention In an engine of thetype described, the main shaft transpierces the end walls of the housingon the longitudinal axis thereof, and has an eccentric portion disposedwithin the housing cavity, on which eccentric the rotor is mounted. Therotor rotates around the eccentric, the axis of which is displaced fromthe shaft axis and planetates therearound. Each of the rotor apexes hasa longitudinally extending slot in which is disposed an apex seal strip,which seal strips sweep the epitrochoidal inner surface of theperipheral housing in sealing relation thereto, the seal strips beingresiliently urged radially into contact with the housing. During theexpansion phase the power stroke is transmitted by the rotor to theeccentric, which in turn revolves the shaft. Although the power istransmitted directly from the rotor to the eccentric, the rotor isnevertheless maintained in precise phase with the epitrochoidal housingby a gearing arrangement. A spur gear surrounds the main shaft and isnonrotatably fixed to an end wall of the housing. The rotor bears a ringgear in engagement with the fixed gear, allowing the rotor axis toplanetate around the shaft axis while maintaining the rotor in itscorrect orientation to the housing. In the embodiment herein described,having a two-lobed epitrochoidal housing and a three-apexed rotor, thering gear has a ratio of 3:2 with the fixed gear, and the shaft turnsthree revolutions for each revolution of the rotor within the housing,although engines having epitrochoids of a different number of lobes willhave other ratios.

Shortly after combustion is initiated, pressure builds up very rapidlyin the working chamber, causing a pressure shock to the rotor in adirection transverse to the shaft. The engine is assembled with certainoperating clearances present in the rotor bearing which is mounted onthe eccentric, and in the main shaft bearings which are mounted in theend walls of the housing, and also in intermediate walls in a multi-unitengine. In addition, the shaft itself may be slightly deflectable.

The combination of these clearances and possible deflections, slightthough they are, may be sufficient that at 3,465,729 Patented Sept. 9,1969 ice the moment of pressure shock one or more of the apex seals iswithdrawn from contact with the peripheral housing, resulting in a lossof pressure from the expanding chamber. Further, on the rebound from thepressure shock the withdrawn seal strikes the housing sharply, resultingin excessive wear of the seal strip.

This condition is overcome in the present invention by indexing eitherthe spur gear fixed to the housng, or the ring gear borne by the rotor,in such a manner that the housing is in a slightly angularly retardedposition with respect to its theoretical position, or the rotor isslightly angularly advanced. Either type of indexing has the same resultwith regard to the relative orientation of the rotor and housing,bringing a slightly different portion of the curvature of the housingadjacent to the affected seal, whereby leakage and wear are avoided.

Brief description of the drawings The invention will be betterunderstood on reading the following specification in conjunction withthe annexed drawings, in which FIG. 1 is an elevational cross-sectiontransverse to the axis of such an engine of the prior art, shown nearthe beginning of combustion and illustrating the defect;

FIG. 2 is a similar view of the improvement of this invention, taken online 22 of FIG. 3;

FIG. 3 is a cross-section elevation of the improved engine on the axialplane;

FIG. 4 is a fragmentary view of a reoriented spur gear, taken on line4-4 of FIG. 3; and

FIG. 5 is a view of the rotor taken on line 55 of FIG. 3 showing areoriented rotor gear.

Description of the preferred embodiments In FIG. 1 there is shown aconventional rotary engine, having a basically epitrochoidal peripheralhousing 11 of two lobes, closed by a pair of parallel end walls of whichonly the rear wall 12 is shown, the front Wall being removed. Intakeport 13 and exhaust port 14 are shown in the peripheral wall, althoughsuch ports may also be provided in one or both end walls. A spark plug16 is shown mounted on the peripheral wall in the region of one cusp ofthe epitrochoid, although the spark plug also may be positioned in oneor both end walls.

A generally triangular rotor 17 is shown within the housing cavity,having a longitudinally extending slot at each apex, containing apexseal strips 18a, 18b, and 18c. The apex seals are permitted a certainamount of radial movement Within their slots, and have springs -19positioned in the slots under the seals, resiliently urging the sealsradially outwardly. Dash-dot line 21 indicates the pitch circle of thespur gear mounted on wall 12, and dash-dot line 22 is the pitch circleof the ring gear borne on the rear face of rotor 17 in mesh with thefixed gear.

The true epitrochoid is shown by the dotted line 23, it being customaryin engines of this type for the inner surface 24 of the peripheral wallto have a curvature parallel to the true epitrochoid and spacedoutwardly therefrom. Such an arrangement allows the rotor to run withits actual apexes at or near the true epitrochoid, and the protrudingapex seals to sweep the inner surface 24 in sealing relation, and alsoallows for some radial movement of the seals in their slots owing toslight manufac turing tolerances in the engine.

In operation the movement of the rotor takes in fresh gas through theintake port 13. As the rotor turns further (clockwise as shown) theintake port is closed by the trailing seal and compression begins. Fullcompression is achieved when the rotor face of the compressing chamberreaches top dead center, slightly counter-clockwise from the rotorposition shown. Ignition usually takes place a little in advance of topdead center.

Upon ignition, combustion pressure builds up very rapidly in the firingchamber, as shown by the pressure arrows 26 normal to the rotor face inthe top chamber shown in the drawing. The sudden pressure build-upoccurring by about the time the rotor has reached the position showncauses a shock transverse to the shaft which drives the rotor downwardin the housing to the position shown, owing to the bearing clearancesand possible shaft deflection previously described. The actual movementof the rotor transversely to the axis is small, amounting only to somethousandths of an inch, but the proportions have been greatlyexaggerated in the drawing for clarity of illustration.

At this portion of the combustion cycle the trailing seal 18a of thefiring chamber is pressed firmly against its slot wall by the pressureof expanding gas, which may be sufficient to lock it firmly in place sothat its spring 19 may not be strong enough to urge it radially intocontact with the peripheral wall. The spring force of springs 19 is keptreasonably light in order to avoid excessive wear of the seals andhousing.

In such circumstances the trailing seal 18a may lose contact with theperipheral housing so that gas pressure is lost across the edge of theseal, as shown by the arrow. The same locked condition may also occur inthe case of the leading seal 18b, but owing to the angle of itsorientation to the peripheral housing surface at this point it is lesslikely to lose contact. At the same time, the seal 180 at the oppositerotor apex is driven sharply into its slot. In reaction to the pressureshock the rotor then immediately rebounds, whereupon seal 18a strikesthe housing surface sharply. There may be a succession of progressivelydamping rebounds, which causes seal wear and chatter marks in thehousing surface.

This condition is corrected by the present invention as shown in FIG. 2,wherein the phasing of the peripheral housing and the rotor is alteredby a slight angular amount to bring a differently curved portion of theinner surface of the peripheral housing opposite the seals at the momentof pressure shock, without significant alteration of the timing of theengine. The phase alteration is accomplished by rotating the housingslightly in a direction opposite to the direction of rotor rotation, orby rotating the rotor slightly on the eccentric in the same direction asrotor rotation. These directions will be hereinafter referred to asupstream rotation for the housing and downstream rotation for the rotor.

In the prior art engines the rotor and housing have been phased togetherso that the rotor turned on the true epitrochoidal path parallel to theouter curve of the peripheral housing. With the rephasing of the presentinvention, the rotor still turns on an epitrochoidal path, but it is nolonger quite parallel to the housing, but is rotated slightlydownstream. The amount of displacement is slight, and well within theaccommodation provided by the radial travel of the apex seals in theirslots. However, it brings the apex seals at the moment of pressure shockadjacent to somewhat differently curved portions of the housing so thatin spite of some displacement of the rotor axis the seals will stillmake proper contact.

In FIG. 2 the rotor is shown at the same period in the combustion cycleas in FIG. 1, that is, at the moment of pressure shock. However, thehousing has been rotated upstream, or the rotor downstream, by the meanslater to be described. Either adjustment produces the same result withregard to the mutual phasing of rotor and housing.

The amount of such relative rotation is indicated by the angle betweenthe lines 27 and 27a, showing respectively the minor diameter of thetrochoidal profile of the housing and of the trochoidal path traversedby the rotor. Angle 0 is preferably about 035, but has a usable range ofplus or minus 025 that is, from about 010 to about 060 over-all.

The epitrochoidal path 23a traversed by the motor tips retains the sameconfiguration and dimensions as before,

but it will be observed that it is now displaced angularly downstreamwith respect to the housing. The trailing seal 18a of the firing chamberhas traveled a little closer to the cusp of the epitrochoid, and sealhas traveled further beyond the other cusp of the epitrochoid, than isthe case in the prior art engine of FIG. 1. Hence, seal 18a is notwithdrawn from contact with the housing surface and there is no leakageof pressure, and seal 180 is not driven so far into its slot, obviatingthe danger of bottoming. The angle of seal 13b to the peripheral housingis not much affected.

FIG. 3 is a cross-sectional elevation of the engine on the axial plane,showing the housing and rotor, shaft 28 having an eccentric portion 29disposed within the housing on which the rotor turns, and the gears andtheir mountings by means of which phasing is accomplished. End wall 12has an axial bore 30 therethrough, in which is positioned the hub 31 ofa spur gear 32 surrounding shaft 28. The hub 31 has a flange 33 by whichit is mounted on the wall 12 by bolts 34 or other convenient fasteningmeans. The outer diameter of hub 31 has a close fit with bore 30, andthe angular position of the gear is established by means of that closefit and a locating dowel 36 through the flange into a bore in the endwall. The rotor bears in a cavity in one end face a ring gear 37, inmesh with spur gear 32. Ring gear 37 is located angularly on the rotorby one or more dowels 38 through the gear body and seated in bores inthe rotor.

FIG. 4 shows one method of rephasing the housing and rotor, by rotatingor displacing the housing angularly upstream relative to the spur gear32, or by rotating the gear angularly downstream in its position on theend wall 12, which amounts to the same thing. The locating dowel 36a isshown in its new position, the former position being indicated by thedotted circle at 36, angularly displaced from the new position by theamount of angle 0. Such relocation may be achieved either by retainingthe dowel bore through flange 33 in its original position with respectto the gear teeth and relocating the dowel bore in end wall 12, or byretaining the seating bore in the end wall and relocating the dowel borethrough the flange, so that the gear teeth are angularly repositionedwith regard to the housing.

FIG. 5 shows another method of rephasing, by rotating the rotor in thedownstream direction with respect to the teeth of its ring gear 37. Thatis, the gear is pinned to the rotor with the teeth slightly upstreamfrom their former position. Dowels 38a are shown in their new position,with the former position indicated by the dotted circles 38, separatedfrom the new position by the angular amount 0. Here again, the dowelseats in the rotor may be relocated and the dowel bores in the gearretained, or the dowel seats may be the same as before and the bores inthe gear relocated, which has the effect of repositioning the rotor in adownstream direction with regard to its gear teeth and hence in regardto the peripheral housing.

The same over-all result may be achieved by rotating both the housingand the rotor as shown in FIGS. 4 and 5, the desired total angle 0 beingdivided between housing rotation and rotor rotation. In both FIGS. 4 and5 the effect is much exaggerated in the drawings, the actual amount ofangular displacement being the selected angle 0 between centerlines, aspreviously set forth.

Although the invention has been described above in preferredembodiments, it is not intended to limit the invention to those preciseembodiments shown and described. It will be understood that variousmodifications may be made without departing from the scope of theinvention as defined in the appended claims.

What is claimed is:

1. A rotary engine having a peripheral housing with an inner surfacehaving a basically epitrochoidal profile, the peripheral housing beingclosed by a pair of parallel end walls to form a cavity therein, a shafttranspiercing the end walls on the axis of the epitrochoid and having aneccentric portion disposed within the cavity, the eccentric having alongitudinal axis parallel to the housing, axis and displaced therefromand planetating therearound, a rotor having a plurality of apexesrotatably mounted on the eccentric, the rotor tracing an epitrochoidalpath within the housing, the rotor path being of the same general formas the housing profile but angularly displaced therefrom.

2. The combination recited in claim 1, wherein the rotor path isangularly displaced downstream from about 010 to about 060.

3. The combination recited in claim 2 wherein the rotor path isangularly displaced downstream about 035.

4. The combination recited in claim 1, wherein one end wall bears a spurgear rigidly mounted thereon and coaxial with the shaft, the rotor bearsa ring gear rigidly mounted thereon and coaxial with the eccentric, themounting of at least one of the gears being positioned to cause therotor to trace an epitrochoidal path out of parallel to the peripheralhousing.

5. The combination recited in claim 4, wherein the mounting of the spurgear is positioned to cause the rotor to trace an epitrochoidal path outof parallel with the peripheral housing.

6. The combination recited in claim 5, wherein the mounting of the ringgear is positioned to cause the rotor to trace an epitrochoidal path outof parallel with the peripheral housing.

7. The combination recited in claim 4, wherein the epitrochoidal path ofthe rotor is angularly displaced downstream from the peripheral housingprofile about 010 to about 060.

8. The combination recited in claim 7, wherein the epitrochoidal path ofthe rotor is angularly displaced downstream from the peripheral housingprofile about 035.

References Cited UNITED STATES PATENTS 3,139,072 6/1964 Froede.3,239,135 3/1966 Fritz. 3,259,114 7/1966 Gassmann.

C. J. HUSAR, Primary Examiner U.S. Cl. X.R. 230-

